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Date: Wed, 4 Jan 2012 00:57:11 +0100
From: Dave Taht <dave.taht@...il.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Michal Kubeček <mkubecek@...e.cz>,
netdev@...r.kernel.org,
"John A. Sullivan III" <jsullivan@...nsourcedevel.com>
Subject: Re: [RFC] SFQ planned changes
On Tue, Jan 3, 2012 at 5:08 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Here is the code I ran on my test server with 200 netperf TCP_STREAM
> flows with pretty good results (each flow gets 0.5 % of bandwidth)
Can I encourage you to always simultaneously run a fping and/or a
netperf -t TCP_RR
latency under load test when doing stuff like this?
The amount of backlogged bytes is rather impressive...
>
> $TC qdisc add dev $DEV root handle 1: est 1sec 8sec htb default 1
> $TC class add dev $DEV parent 1: classid 1:1 est 1sec 8sec htb \
> rate 200Mbit mtu 40000 quantum 80000
>
> $TC qdisc add dev $DEV parent 1:1 handle 10: est 1sec 8sec sfq \
> limit 2000 depth 10 headdrop flows 1000 divisor 16384
>
> # tcnew -s -d qdisc show dev eth3
> qdisc htb 1: root refcnt 18 r2q 10 default 1 direct_packets_stat 0 ver 3.17
> Sent 4512949730 bytes 3030391 pkt (dropped 44409, overlimits 6105100 requeues 1)
> rate 198288Kbit 16629pps backlog 0b 1732p requeues 1
> qdisc sfq 10: parent 1:1 limit 2000p quantum 1514b depth 10 headdrop flows 1000/16384 divisor 16384
> Sent 4512949730 bytes 3030391 pkt (dropped 44409, overlimits 0 requeues 0)
> rate 198288Kbit 16629pps backlog 2622248b 1732p requeues 0
>
> patch on top of current net-next
I'm not going to have time to get to this for a while...
> include/linux/pkt_sched.h | 7 +
> net/sched/sch_sfq.c | 144 ++++++++++++++++++++++++------------
> 2 files changed, 104 insertions(+), 47 deletions(-)
>
> diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
> index 8daced3..c2c6cfd 100644
> --- a/include/linux/pkt_sched.h
> +++ b/include/linux/pkt_sched.h
> @@ -162,6 +162,13 @@ struct tc_sfq_qopt {
> unsigned flows; /* Maximal number of flows */
> };
>
> +struct tc_sfq_ext_qopt {
> + struct tc_sfq_qopt qopt;
> + unsigned int depth; /* max number of packets per flow */
> + unsigned int headdrop;
> +};
> +
> +
> struct tc_sfq_xstats {
> __s32 allot;
> };
> diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
> index d329a8a..66682fd 100644
> --- a/net/sched/sch_sfq.c
> +++ b/net/sched/sch_sfq.c
> @@ -67,15 +67,16 @@
>
> IMPLEMENTATION:
> This implementation limits maximal queue length to 128;
> - max mtu to 2^18-1; max 128 flows, number of hash buckets to 1024.
> - The only goal of this restrictions was that all data
> - fit into one 4K page on 32bit arches.
> + max mtu to 2^18-1;
> + max 65280 flows,
> + number of hash buckets to 65536.
>
> It is easy to increase these values, but not in flight. */
>
> #define SFQ_DEPTH 128 /* max number of packets per flow */
> -#define SFQ_SLOTS 128 /* max number of flows */
> -#define SFQ_EMPTY_SLOT 255
> +#define SFQ_DEFAULT_FLOWS 128
> +#define SFQ_MAX_FLOWS (0x10000 - 256) /* max number of flows */
> +#define SFQ_EMPTY_SLOT 0xffff
> #define SFQ_DEFAULT_HASH_DIVISOR 1024
>
> /* We use 16 bits to store allot, and want to handle packets up to 64K
> @@ -84,13 +85,13 @@
> #define SFQ_ALLOT_SHIFT 3
> #define SFQ_ALLOT_SIZE(X) DIV_ROUND_UP(X, 1 << SFQ_ALLOT_SHIFT)
>
> -/* This type should contain at least SFQ_DEPTH + SFQ_SLOTS values */
> -typedef unsigned char sfq_index;
> +/* This type should contain at least SFQ_DEPTH + SFQ_MAX_FLOWS values */
> +typedef u16 sfq_index;
>
> /*
> * We dont use pointers to save space.
> - * Small indexes [0 ... SFQ_SLOTS - 1] are 'pointers' to slots[] array
> - * while following values [SFQ_SLOTS ... SFQ_SLOTS + SFQ_DEPTH - 1]
> + * Small indexes [0 ... SFQ_MAX_FLOWS - 1] are 'pointers' to slots[] array
> + * while following values [SFQ_MAX_FLOWS ... SFQ_MAX_FLOWS + SFQ_DEPTH - 1]
> * are 'pointers' to dep[] array
> */
> struct sfq_head {
> @@ -112,8 +113,11 @@ struct sfq_sched_data {
> /* Parameters */
> int perturb_period;
> unsigned int quantum; /* Allotment per round: MUST BE >= MTU */
> - int limit;
> + int limit; /* limit of total number of packets in this qdisc */
> unsigned int divisor; /* number of slots in hash table */
> + unsigned int maxflows; /* number of flows in flows array */
> + int headdrop;
> + int depth; /* limit depth of each flow */
> /* Variables */
> struct tcf_proto *filter_list;
> struct timer_list perturb_timer;
> @@ -122,7 +126,7 @@ struct sfq_sched_data {
> unsigned short scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
> struct sfq_slot *tail; /* current slot in round */
> sfq_index *ht; /* Hash table (divisor slots) */
> - struct sfq_slot slots[SFQ_SLOTS];
> + struct sfq_slot *slots;
> struct sfq_head dep[SFQ_DEPTH]; /* Linked list of slots, indexed by depth */
> };
>
> @@ -131,9 +135,9 @@ struct sfq_sched_data {
> */
> static inline struct sfq_head *sfq_dep_head(struct sfq_sched_data *q, sfq_index val)
> {
> - if (val < SFQ_SLOTS)
> + if (val < SFQ_MAX_FLOWS)
> return &q->slots[val].dep;
> - return &q->dep[val - SFQ_SLOTS];
> + return &q->dep[val - SFQ_MAX_FLOWS];
> }
>
> /*
> @@ -199,18 +203,19 @@ static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
> }
>
> /*
> - * x : slot number [0 .. SFQ_SLOTS - 1]
> + * x : slot number [0 .. SFQ_MAX_FLOWS - 1]
> */
> static inline void sfq_link(struct sfq_sched_data *q, sfq_index x)
> {
> sfq_index p, n;
> - int qlen = q->slots[x].qlen;
> + struct sfq_slot *slot = &q->slots[x];
> + int qlen = slot->qlen;
>
> - p = qlen + SFQ_SLOTS;
> + p = qlen + SFQ_MAX_FLOWS;
> n = q->dep[qlen].next;
>
> - q->slots[x].dep.next = n;
> - q->slots[x].dep.prev = p;
> + slot->dep.next = n;
> + slot->dep.prev = p;
>
> q->dep[qlen].next = x; /* sfq_dep_head(q, p)->next = x */
> sfq_dep_head(q, n)->prev = x;
> @@ -305,7 +310,7 @@ static unsigned int sfq_drop(struct Qdisc *sch)
> x = q->dep[d].next;
> slot = &q->slots[x];
> drop:
> - skb = slot_dequeue_tail(slot);
> + skb = q->headdrop ? slot_dequeue_head(slot) : slot_dequeue_tail(slot);
> len = qdisc_pkt_len(skb);
> sfq_dec(q, x);
> kfree_skb(skb);
> @@ -349,16 +354,26 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
> slot = &q->slots[x];
> if (x == SFQ_EMPTY_SLOT) {
> x = q->dep[0].next; /* get a free slot */
> + if (x >= SFQ_MAX_FLOWS)
> + return qdisc_drop(skb, sch);
> q->ht[hash] = x;
> slot = &q->slots[x];
> slot->hash = hash;
> }
>
> - /* If selected queue has length q->limit, do simple tail drop,
> - * i.e. drop _this_ packet.
> - */
> - if (slot->qlen >= q->limit)
> - return qdisc_drop(skb, sch);
> + if (slot->qlen >= q->depth) {
> + struct sk_buff *head;
> +
> + if (!q->headdrop)
> + return qdisc_drop(skb, sch);
> + head = slot_dequeue_head(slot);
> + sch->qstats.backlog -= qdisc_pkt_len(head);
> + kfree_skb(head);
> + sch->qstats.drops++;
> + sch->qstats.backlog += qdisc_pkt_len(skb);
> + slot_queue_add(slot, skb);
> + return NET_XMIT_CN;
> + }
>
> sch->qstats.backlog += qdisc_pkt_len(skb);
> slot_queue_add(slot, skb);
> @@ -366,11 +381,11 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
> if (slot->qlen == 1) { /* The flow is new */
> if (q->tail == NULL) { /* It is the first flow */
> slot->next = x;
> + q->tail = slot;
> } else {
> slot->next = q->tail->next;
> q->tail->next = x;
> }
> - q->tail = slot;
> slot->allot = q->scaled_quantum;
> }
> if (++sch->q.qlen <= q->limit)
> @@ -445,16 +460,17 @@ sfq_reset(struct Qdisc *sch)
> * We dont use sfq_dequeue()/sfq_enqueue() because we dont want to change
> * counters.
> */
> -static void sfq_rehash(struct sfq_sched_data *q)
> +static int sfq_rehash(struct sfq_sched_data *q)
> {
> struct sk_buff *skb;
> int i;
> struct sfq_slot *slot;
> struct sk_buff_head list;
> + int dropped = 0;
>
> __skb_queue_head_init(&list);
>
> - for (i = 0; i < SFQ_SLOTS; i++) {
> + for (i = 0; i < q->maxflows; i++) {
> slot = &q->slots[i];
> if (!slot->qlen)
> continue;
> @@ -474,6 +490,11 @@ static void sfq_rehash(struct sfq_sched_data *q)
> slot = &q->slots[x];
> if (x == SFQ_EMPTY_SLOT) {
> x = q->dep[0].next; /* get a free slot */
> + if (x >= SFQ_MAX_FLOWS) {
> + kfree_skb(skb);
> + dropped++;
> + continue;
> + }
> q->ht[hash] = x;
> slot = &q->slots[x];
> slot->hash = hash;
> @@ -491,6 +512,7 @@ static void sfq_rehash(struct sfq_sched_data *q)
> slot->allot = q->scaled_quantum;
> }
> }
> + return dropped;
> }
>
> static void sfq_perturbation(unsigned long arg)
> @@ -502,7 +524,7 @@ static void sfq_perturbation(unsigned long arg)
> spin_lock(root_lock);
> q->perturbation = net_random();
> if (!q->filter_list && q->tail)
> - sfq_rehash(q);
> + qdisc_tree_decrease_qlen(sch, sfq_rehash(q));
> spin_unlock(root_lock);
>
> if (q->perturb_period)
> @@ -513,11 +535,13 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
> {
> struct sfq_sched_data *q = qdisc_priv(sch);
> struct tc_sfq_qopt *ctl = nla_data(opt);
> + struct tc_sfq_ext_qopt *ctl_ext = NULL;
> unsigned int qlen;
>
> if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
> return -EINVAL;
> -
> + if (opt->nla_len >= nla_attr_size(sizeof(*ctl_ext)))
> + ctl_ext = nla_data(opt);
> if (ctl->divisor &&
> (!is_power_of_2(ctl->divisor) || ctl->divisor > 65536))
> return -EINVAL;
> @@ -526,10 +550,18 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
> q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
> q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
> q->perturb_period = ctl->perturb_period * HZ;
> - if (ctl->limit)
> - q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1);
> + if (ctl->flows)
> + q->maxflows = min_t(u32, ctl->flows, SFQ_MAX_FLOWS);
> if (ctl->divisor)
> q->divisor = ctl->divisor;
> + if (ctl_ext) {
> + if (ctl_ext->depth)
> + q->depth = min_t(u32, ctl_ext->depth, SFQ_DEPTH - 1);
> + q->headdrop = ctl_ext->headdrop;
> + }
> + if (ctl->limit)
> + q->limit = min_t(u32, ctl->limit, q->depth * q->maxflows);
> +
> qlen = sch->q.qlen;
> while (sch->q.qlen > q->limit)
> sfq_drop(sch);
> @@ -544,6 +576,16 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
> return 0;
> }
>
> +static void sfq_free(void *addr)
> +{
> + if (addr) {
> + if (is_vmalloc_addr(addr))
> + vfree(addr);
> + else
> + kfree(addr);
> + }
> +}
> +
> static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
> {
> struct sfq_sched_data *q = qdisc_priv(sch);
> @@ -555,14 +597,16 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
> init_timer_deferrable(&q->perturb_timer);
>
> for (i = 0; i < SFQ_DEPTH; i++) {
> - q->dep[i].next = i + SFQ_SLOTS;
> - q->dep[i].prev = i + SFQ_SLOTS;
> + q->dep[i].next = i + SFQ_MAX_FLOWS;
> + q->dep[i].prev = i + SFQ_MAX_FLOWS;
> }
>
> q->limit = SFQ_DEPTH - 1;
> + q->depth = SFQ_DEPTH - 1;
> q->cur_depth = 0;
> q->tail = NULL;
> q->divisor = SFQ_DEFAULT_HASH_DIVISOR;
> + q->maxflows = SFQ_DEFAULT_FLOWS;
> if (opt == NULL) {
> q->quantum = psched_mtu(qdisc_dev(sch));
> q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
> @@ -575,15 +619,22 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
> }
>
> sz = sizeof(q->ht[0]) * q->divisor;
> - q->ht = kmalloc(sz, GFP_KERNEL);
> + q->ht = kmalloc(sz, GFP_KERNEL | __GFP_NOWARN);
> if (!q->ht && sz > PAGE_SIZE)
> q->ht = vmalloc(sz);
> if (!q->ht)
> return -ENOMEM;
> +
> + q->slots = kzalloc(sizeof(q->slots[0]) * q->maxflows, GFP_KERNEL | __GFP_NOWARN);
> + if (!q->slots)
> + q->slots = vzalloc(sizeof(q->slots[0]) * q->maxflows);
> + if (!q->slots) {
> + sfq_free(q->ht);
> + return -ENOMEM;
> + }
> for (i = 0; i < q->divisor; i++)
> q->ht[i] = SFQ_EMPTY_SLOT;
> -
> - for (i = 0; i < SFQ_SLOTS; i++) {
> + for (i = 0; i < q->maxflows; i++) {
> slot_queue_init(&q->slots[i]);
> sfq_link(q, i);
> }
> @@ -601,25 +652,24 @@ static void sfq_destroy(struct Qdisc *sch)
> tcf_destroy_chain(&q->filter_list);
> q->perturb_period = 0;
> del_timer_sync(&q->perturb_timer);
> - if (is_vmalloc_addr(q->ht))
> - vfree(q->ht);
> - else
> - kfree(q->ht);
> + sfq_free(q->ht);
> + sfq_free(q->slots);
> }
>
> static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb)
> {
> struct sfq_sched_data *q = qdisc_priv(sch);
> unsigned char *b = skb_tail_pointer(skb);
> - struct tc_sfq_qopt opt;
> -
> - opt.quantum = q->quantum;
> - opt.perturb_period = q->perturb_period / HZ;
> + struct tc_sfq_ext_qopt opt;
>
> - opt.limit = q->limit;
> - opt.divisor = q->divisor;
> - opt.flows = q->limit;
> + opt.qopt.quantum = q->quantum;
> + opt.qopt.perturb_period = q->perturb_period / HZ;
>
> + opt.qopt.limit = q->limit;
> + opt.qopt.divisor = q->divisor;
> + opt.qopt.flows = q->maxflows;
> + opt.depth = q->depth;
> + opt.headdrop = q->headdrop;
> NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
>
> return skb->len;
>
>
--
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
FR Tel: 0638645374
http://www.bufferbloat.net
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